Make sure that your quotes are straight quotes instead of curly quotes. Airtable’s formula engine doesn’t recognize anything except for straight quotes.

Hmm, well aren’t these straight quotes … symbol under double quote on my keyboard.

DATETIME_DIFF(TODAY(),PROMOEND,’months’)

@J_Allen, the difference is that those curly quotes are rich-text, while the straight ones are plain-text.

Big pain in the bottom, but avoided by copy/pasting from a plain-text editor like notepad. If you put it in microsoft word or something like that, the straight quotes get converted to those curly quotes.

Thanks Kris. So I used my Mac vs iPad (the Airtable app) and though the same exact key on the keyboard was used, that worked. Perhaps a nuanced difference in iOS Safari > Airtable.com vs. macOS > Airtable app … but one would expect it would have worked.